Why Do We Use AM and PM?
It is part of our lives to use AM to refer to the morning time and PM for the afternoon. But, what is its origin? We have to start first with the M part. M stands for meridian. The word meridian (Latin meridiem) refers to an imaginary line which runs from north to south, always perpendicular to the latitude lines. In the northern hemisphere, if we face south during a clear day we will notice that the sun describes an arch that goes roughly from east to west. The highest point of the sun is reached when it is exactly south, at approximately noon. At that time of the day, the sun effectively "crosses the meridian line". In Latin, the word ante means before and the word post means after. So, if we refer to the position of the sun in the morning, it would be ante meridiem (AM) and in the afternoon it would be post meridiem (PM)
